linux-kernel - [RFC PATCH v2 5/9] iommu/arm-smmu-v3: Alloc vmid from global pool

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Message-ID: <20230822185632.RFC.v2.5.If0dc099688d13ce9e661a1e4a1339030f243ff39@changeid>
Date:   Tue, 22 Aug 2023 18:57:01 +0800
From:   Michael Shavit <mshavit@...gle.com>
To:     iommu@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Cc:     nicolinc@...dia.com, tina.zhang@...el.com,
        jean-philippe@...aro.org, will@...nel.org, robin.murphy@....com,
        jgg@...dia.com, Michael Shavit <mshavit@...gle.com>,
        Dawei Li <set_pte_at@...look.com>,
        Jason Gunthorpe <jgg@...pe.ca>, Joerg Roedel <joro@...tes.org>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        Mark Brown <broonie@...nel.org>
Subject: [RFC PATCH v2 5/9] iommu/arm-smmu-v3: Alloc vmid from global pool

Consistent with how ASIDs are allocated, allocate VMIds from a global
pool instead of a per-SMMU pool. This allows the domain to be attached
onto multiple SMMUs.

Signed-off-by: Michael Shavit <mshavit@...gle.com>
---
As discussed in v1 RFC, an alternative would be to support assigning a
different VMID/ASID to a domain for each SMMU that it is installed to.
This is more flexible but will require more work to achieve.

(no changes since v1)

 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 10 +++-------
 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h |  1 -
 2 files changed, 3 insertions(+), 8 deletions(-)

diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
index 1d072fd38a2d6..9adc2cedd487b 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
@@ -73,6 +73,7 @@ struct arm_smmu_option_prop {
 
 DEFINE_XARRAY_ALLOC1(arm_smmu_asid_xa);
 DEFINE_MUTEX(arm_smmu_asid_lock);
+DEFINE_IDA(arm_smmu_vmid_ida);
 
 /*
  * Special value used by SVA when a process dies, to quiesce a CD without
@@ -2130,7 +2131,6 @@ static struct iommu_domain *arm_smmu_domain_alloc(unsigned type)
 static void arm_smmu_domain_free(struct iommu_domain *domain)
 {
 	struct arm_smmu_domain *smmu_domain = to_smmu_domain(domain);
-	struct arm_smmu_device *smmu = smmu_domain->smmu;
 
 	free_io_pgtable_ops(smmu_domain->pgtbl_ops);
 
@@ -2143,7 +2143,7 @@ static void arm_smmu_domain_free(struct iommu_domain *domain)
 	} else {
 		struct arm_smmu_s2_cfg *cfg = &smmu_domain->s2_cfg;
 		if (cfg->vmid)
-			ida_free(&smmu->vmid_map, cfg->vmid);
+			ida_free(&arm_smmu_vmid_ida, cfg->vmid);
 	}
 
 	kfree(smmu_domain);
@@ -2195,7 +2195,7 @@ static int arm_smmu_domain_finalise_s2(struct arm_smmu_domain *smmu_domain,
 	typeof(&pgtbl_cfg->arm_lpae_s2_cfg.vtcr) vtcr;
 
 	/* Reserve VMID 0 for stage-2 bypass STEs */
-	vmid = ida_alloc_range(&smmu->vmid_map, 1, (1 << smmu->vmid_bits) - 1,
+	vmid = ida_alloc_range(&arm_smmu_vmid_ida, 1, (1 << smmu->vmid_bits) - 1,
 			       GFP_KERNEL);
 	if (vmid < 0)
 		return vmid;
@@ -3169,9 +3169,6 @@ static int arm_smmu_init_strtab(struct arm_smmu_device *smmu)
 	reg  = smmu->strtab_cfg.strtab_dma & STRTAB_BASE_ADDR_MASK;
 	reg |= STRTAB_BASE_RA;
 	smmu->strtab_cfg.strtab_base = reg;
-
-	ida_init(&smmu->vmid_map);
-
 	return 0;
 }
 
@@ -3995,7 +3992,6 @@ static void arm_smmu_device_remove(struct platform_device *pdev)
 	iommu_device_sysfs_remove(&smmu->iommu);
 	arm_smmu_device_disable(smmu);
 	iopf_queue_free(smmu->evtq.iopf);
-	ida_destroy(&smmu->vmid_map);
 }
 
 static void arm_smmu_device_shutdown(struct platform_device *pdev)
diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
index b0cf9c33e6bcd..1661d3252bac5 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
@@ -670,7 +670,6 @@ struct arm_smmu_device {
 
 #define ARM_SMMU_MAX_VMIDS		(1 << 16)
 	unsigned int			vmid_bits;
-	struct ida			vmid_map;
 
 	unsigned int			ssid_bits;
 	unsigned int			sid_bits;
-- 
2.42.0.rc1.204.g551eb34607-goog